Fault-Tolerant Self-Tuning Control for Three-Phase Three-Level T-Type Rectifier

This article proposes a sensorless self-tuning control algorithm for a three-phase T-type rectifier. The proposed sensorless algorithm consists of three layers including an observer, which estimates grid voltages or currents based on the Kalman filter algorithm, an online estimator, which estimates the state-space matrix parameters, and a linear quadratic tracker (LQT), which is the main controller in this article. On the other hand, the performance of the LQT depends on the gains that need to be adjusted according to the system parameters, which is a challenge. To overcome this problem, a self-tuning method based on recursive least square algorithm is also proposed to tune the gains of LQT online. An experimental prototype is established, and the results, including the steady state and dynamic performances, are carried out and presented to validate the effectiveness of the proposed controller.